Petkovic kept up with Williams until 4-4 in the final set. Then she dropped her serve and Williams closed out the match in 2 hours, 38 minutes.

"She's such a tough opponent - I just had to keep fighting," Williams said. "She was playing so well and attacking all the time, and the only thing you can do in a match like that is just try to win more points than your opponent - that's all I tried to do, just keep coming back, coming back, and winning more points."

"This was the first tournament since I came back that I felt like the old Andrea Petkovic," Petko said. "That's very important for me because I was doubting myself the last few weeks. I feel better about my game now; I feel like I can get back to the high level I had again."

"Unfortunately I will not be able to return in time for Wimbledon this year. While this is another setback in my return, I will continue to work hard on getting back on court as soon as possible," Petkovic said.